Will 2-D tin be the next super material?

November 21, 2013

A single layer of tin -- an element familiar as the coating for tin cans -- could be the world's first material to conduct electricity with 100 percent efficiency at the temperatures that computer chips operate, according to a team led by researchers from the US Department of Energy's SLAC National Accelerator Laboratory and Stanford University. If used as wiring in computer chips, the material, called "stanene," could increase the speed and lower the power needs of future generations of computers. Credit: Brad Plummer/SLAC

A single layer of tin atoms could be the world's first material to conduct electricity with 100 percent efficiency at the temperatures that computer chips operate, according to a team of theoretical physicists led by researchers from the U.S. Department of Energy's (DOE) SLAC National Accelerator Laboratory and Stanford University.

Researchers call the new material "stanene," combining the Latin name for tin (stannum) with the suffix used in graphene, another single-layer material whose novel electrical properties hold promise for a wide range of applications.

"Stanene could increase the speed and lower the power needs of future generations of computer chips, if our prediction is confirmed by experiments that are underway in several laboratories around the world," said the team leader, Shoucheng Zhang, a physics professor at Stanford and the Stanford Institute for Materials and Energy Sciences (SIMES), a joint institute with SLAC. The team's work was published recently in Physical Review Letters.

The Path to Stanene

For the past decade, Zhang and colleagues have been calculating and predicting the electronic properties of a special class of materials known as topological insulators, which conduct electricity only on their outside edges or surfaces and not through their interiors. When topological insulators are just one atom thick, their edges conduct electricity with 100 percent efficiency. These unusual properties result from complex interactions between the electrons and nuclei of heavy atoms in the materials.

Adding fluorine atoms (yellow) to a single layer of tin atoms (gray) should allow a predicted new material, stanene, to conduct electricity perfectly along its edges (blue and red arrows) at temperatures up to 100 degrees Celsius. The first application for this stanene-fluorine combination could be in wiring that connects the many sections of a microprocessor, allowing electrons to flow as easily as cars on a freeway. Credit: Yong Xu/Tsinghua University; Greg Stewart/SLAC

"The magic of topological insulators is that by their very nature, they force electrons to move in defined lanes without any speed limit, like the German autobahn," Zhang said. "As long as they're on the freeway – the edges or surfaces – the electrons will travel without resistance."

In 2006 and 2009, Zhang's group predicted that mercury telluride and several combinations of bismuth, antimony, selenium and tellurium should be topological insulators, and they were soon proven right in experiments performed by others. But none of those materials is a perfect conductor of electricity at room temperature, limiting their potential for commercial applications.

Earlier this year, visiting scientist Yong Xu, who is now at Tsinghua University in Beijing, collaborated with Zhang's group to consider the properties of a single layer of pure tin.

"We knew we should be looking at elements in the lower-right portion of the periodic table," Xu said. "All previous topological insulators have involved the heavy and electron-rich elements located there."

Their calculations indicated that a single layer of tin would be a topological insulator at and above room temperature, and that adding fluorine atoms to the tin would extend its operating range to at least 100 degrees Celsius (212 degrees Fahrenheit).

Ultimately a Substitute for Silicon?

Zhang said the first application for this stanene-fluorine combination could be in wiring that connects the many sections of a microprocessor, allowing electrons to flow as freely as cars on a highway. Traffic congestion would still occur at on- and off-ramps made of conventional conductors, he said. But stanene wiring should significantly reduce the power consumption and heat production of microprocessors.

Manufacturing challenges include ensuring that only a single layer of tin is deposited and keeping that single layer intact during high-temperature chip-making processes.

"Eventually, we can imagine stanene being used for many more circuit structures, including replacing silicon in the hearts of transistors," Zhang said. "Someday we might even call this area Tin Valley rather than Silicon Valley."

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16 comments

The value of tin is going to increase as this technology develops.With the prices of platinum, gold, and silver going through the roof it is good to know there is still a metal that has a lot of positive investment growth potential.

"conduct electricity with 100 percent efficiency at the temperatures that computer chips operate"

So stacks of this would not be considered a room temperature superconductor... why, exactly? Even if stacking stopped the effect, would tubes or other configurations with something used to separate the layers provide the effect? And how do they compare with normal conductors and superconductors as far capacity is concerned? In short, why is this being envisioned as a component of chips instead of components of a tech revolution? Where is the catch?

The value of tin is going to increase as this technology develops.With the prices of platinum, gold, and silver going through the roof it is good to know there is still a metal that has a lot of positive investment growth potential.

I suppose the amount of that increase depends on how many deposits of tin ore are just slightly short of being profitable enough to exploit. I seem to recall Afghanistan being found to be rich in different ores and I think tin was one. It might give people an incentive to stop tolerating extremists in their midst--not to mention the money to pay for less corrupt security personnel.

The value of tin is going to increase as this technology develops.With the prices of platinum, gold, and silver going through the roof it is good to know there is still a metal that has a lot of positive investment growth potential.

not on this planet.... your assumptions are entirely opposite of reality

The topological insulators aren't superconductors - it just means, their surface conductivity is higher, than this bulk one.

I guess I have a less technical understanding of what "conduct electricity with 100 percent efficiency" than the author of the sentence. To a layman that sounds like how superconductors are often described. I can see that this effect would only be present along the strip so every break or gap would return resistance to circuit.

And it occurs to me (after an embarrassingly long time) that my suggested tubes of the stuff would not have this effect since they don't have edges other than their ends (not that tin tubes might not have other interesting properties if they are possible to construct).

I wouldn't bet on it. With the amount of tin produced per year you could cover roughly 10% of the Earth's surface in stanene. That's the cool thing about 2D materials: you really don't need a lot of them.

I suppose the amount of that increase depends on how many deposits of tin ore are just slightly short of being profitable enough to exploit. I seem to recall Afghanistan being found to be rich in different ores and I think tin was one. It might give people an incentive to stop tolerating extremists in their midst--not to mention the money to pay for less corrupt security personnel.

The places with a lot of natural resources tend to be the worst hell holes on Earth.

There are two major reasons for this. The government doesn't have to care what their people think as long as it can support itself on revenue from resources. Resources always attract undue attention from the west; hence we support unspeakable dictators like Saddam and start resource wars like Vietnam(read the Pentagon papers; it was about oil, tin, rubber and strategic military bases in the region).

The biggest challenge as I see it, is that a 1-atom thick layer has very limited current-carrying capacity. I doubt that zero-resistance permits infinite current, but if I'm wrong, I stand to be corrected.

The critical current density of a 1-atom layer would be very low, therefore a conductor would need a very large surface area to be practical for most applications. Perhaps a highly-corrugated design would be required.

The perfect conductivity is only at the edges of strips. So you really want 'd want to have this in a stripe configuration (for serious power transmission you'd need this stacked with intermittent isolation layers). But that's not really what it's for. It would be way too costly to manufacture monolayers in a configuration that would be useful for serious power transmission.

Was the massive initial downvoting of posts triggered by the German autobahn pun

Unfortunately the reality between being allowed to drive any speed clashes with being able to drive any speed (as mostly traffic densities over here don't allow going faster than 130-170km/h... the places where you are allowed to go any speed are getting fewer and fewer as it is)

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